1. Field of the Invention
The present invention relates to apparatus for automatically and manually focusing an adjustable focus lens, in general, and to such apparatus for focusing and adjustable focus lens in a photographic camera having both automatic and manual focusing modes of operation, in particular.
2. Description of the Prior Art
Photographic cameras having both automatic and manual focusing modes of operation are presently available in the prior art. One such camera is sold by the Polaroid Corporation under its registered trademark SX-70 Sonar One-Step. In the automatic focus control mode, a focus control system is coupled to the adjustable focus lens of said camera and positions the lens to a focus position in accordance with an ultrasonic rangefinder derived signal representative of the distance to a subject to be photographed. In the manual focus control mode, an optical rangefinder is coupled to the adjustable focus lens; the automatic focus control system being disabled when said manual focus control mode is selected. A follow-focus arrangement is employed in that aperture adjustment and flash illumination output are mechanically coupled to lens focus position in order to correlate subject distance with the appropriate aperture size and/or flash illumination output.
Providing both automatic and manual focus control capabilities in a photographic camera substantially improves the range of conditions over which a photographic image can be produced and the quality of a photographic print produced with such an image. However, if both automatic and manual focusing capabilities are to be provided in a photographic camera, it would appear that camera size and/or cost would logically have to increase in order to house the hardware that provides such capabilities.
In the photographic camera noted above, for example, camera size and cost are increased when providing these capabilities because hardware employed to provide range information in one camera focusing mode of operation is functionally duplicated with additional hardware when providing the same range information in the other camera focusing mode of operation.